Daniel Keep escribió:
Walter Bright wrote:
Daniel Keep wrote:
That's true, but you haven't addressed the other side of it: property
setters.
Right. Consider the case where there's a pure function with no
arguments, and an overload with the same name and one argument, and no
other overloads. Wouldn't it be reasonable to take that as a property
setter?
With D, you would need to explicitly state which methods are properties
manually somehow; dunno how you would, though. Especially when you
consider subclassing and mixins.
See my rule above - I think it'll work.
Actually, I've now come up with a counter-example for the idea of using
pure at all:
class Lazy(T)
{
private
{
T v;
T delegate() dg;
}
this(T delegate() dg) { this.dg = dg; }
T value()
{
if( dg !is null )
{
v = dg();
dg = null;
}
return v;
}
}
You can't make value pure, but it is supposed to be a property. One of
the examples Nick gives in DIP4 is a property that accesses an SQL
database; there's no way to make that pure!
Exactly! That's why I said "kind of pure" (well, maybe I didn't say that
:-P), but the idea is that properties don't modify anything visible from
outside of the symbol they are contained in. But it's hard to define
what that means...
